Drug allergy: in vitro cross-allergenicity between amoxicillin and benzyl penicillin.

The capacity of amoxicillin to elicit allergenic reactions in vitro was determined on benzyl-penicillin sensitive patients. RAST and histamine release were performed on blood of these patients using B pen linked to human serum albumin (BPO-HSA) as allergen. A relationship was noted between the results of the in vitro tests and the date of the allergic manifestations. When results of RAST and histamine release were significant, amoxicillin was tested for its capacity to elicit histamine release and to inhibit RAST performed with BPO-HSA. A cross-allergenicity was observed in six sera out of eight. The results suggested that amoxicillin may be capable to react with cell-bound or serum IgE to give hypersensitive manifestations in some penicillin sensitive patients.